1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to changing an access point in a wireless network system, and more particularly, to changing an access point in a wireless network system, which can provide an access point having the best performance in a wireless network system and thus improve the transmission efficiency.
2. Description of the Prior Art
The demand for the use of the Internet is increasing, and particularly, the use of the Internet through a wireless LAN is on an increasing trend. A wireless LAN provides services that are provided by a conventional short-distance wire communication, i.e., a wired LAN, by using a wireless medium. A widely-used wireless communication method is the IEEE 802.11 standard.
The wireless LAN service enables a wireless LAN terminal, such as a notebook computer, a PDA, and so forth, to access and receive various types of services, such as wireless Internet services, using an access point that serves as a wired/wireless gateway. The access point plays a role similar to that of a LAN hub, and for one access point, about 25-50 terminals can simultaneously access Internet services in an area having a radius in the range of 20-150 m.
Generally, a wireless LAN system may include several access points that use different channels in an extension service set (ESS), and a wireless LAN terminal in the extension service set performs a scan in order to find out accessible access points. In this case, the scan method may be classified into an active scan method and a passive scan method.
In the active scan method, access points are detected in a manner that a wireless LAN terminal transmits a probe request to the access points and receives probe responses from the access points. In contrast, in the passive scan method, access points are detected in a manner that the access points periodically transmit beacon frames and a wireless LAN terminal receives the transmitted beacon frames. Generally, the active scan method has been used.
As described above, in a general wireless LAN system, a wireless LAN terminal detects accessible access points by using the active scan method. In this case, the wireless LAN terminal selects an access point that has transmitted a probe response having the highest received signal strength indicator (RSSI) among probe responses received from a plurality of access points, transmits an association request to the selected access point, and receives an association response from the access point in response to the association request, so that the wireless LAN terminal and the access point are associated with each other.
However, the apparatus and method of changing an access point in a conventional wireless network system has the following problems.
Even though a user terminal first selects and accesses an access point having a good received signal strength indicator, the communication performance (e.g., bandwidth and so on) may deteriorate later due to an access of another user terminal or due to other reasons.
However, according to the conventional wireless network system, once the user terminal accesses a specified access point, it cannot know or change access to any other accessible access point having a better access environment. Accordingly, even though the user terminal can access another access point to achieve high-quality communications, the user terminal must continuously use the poor-quality wireless service. That is, since the wireless LAN terminal does not intend to access another access point in spite of an overload occurring due to the traffic concentration to one access point and the existence of an adjacent accessible access point having a better access environment, the traffic cannot be effectively distributed in a service area.